Prosthesis suspension liners formed from silicone elastomeric materials have been described in prior patents, such as, for example, U.S. Pat. Nos. 4,923,474, 5,507,834, 5,376,129, 5,658,354, 5,888,216, 6,136,039, and 6,508,842. Elastomeric liners are commonly used to cushion a post-operative stump or residual limb with respect to a prosthesis. The prosthesis will typically include a rigid socket that is shaped to receive the stump or residual limb. The socket is installed over the residual limb and may be coupled to the liner by a locking element.
It is desirable that such liners conform to the outer surface of the residual limb and provide a comfortable cushion between the residual limb and the rigid socket of the prosthesis that is to be fitted over the residual limb. Special silicone rubber or elastomeric materials have been formulated as suitable substances for suspension liners. Such materials are typically selected on the basis of one or more of the following properties: hardness (or softness), elongation, tensile strength, sterilizability, porosity, and ease of cleaning. In particular, composite materials including silicone have been used successfully for suspension liners.
Despite advances in the materials, certain aspects of prosthesis liners remain sub-optimal. One such aspect is the upper or proximal edge of the liner. In instances where die prosthesis is held in place through mechanical engagement between the socket and the liner, the liner is in turn held in place by air pressure. With the limb in place within the liner, the gap between the edge of the liner and the limb is sealed to prevent the ingress of air into the space around the limb. This prevents air from entering the space between the limb and the liner For this reason, the term “suction socket” is occasionally used. The sealing method often requires applying pressure around the upper edge of the liner. However if the upper edge of the liner is not constructed with this consideration in mind, the contact and pressure of the liner edge on the limb can cause extreme discomfort.
Even in instances where a seal is not required, the liner may cause difficulty. For example, the liner may be too long, or may be finished or cut in such a manner that its upper edge causes the wearer discomfort. Hence, it remains highly desirable to provide the amputee with a optimal feeling of comfort at the residual limb interface with the prosthesis while maintaining strength and durability of the liner.